qemuboot.bbclass: Setup the vardeps for write_qemuboot_conf
Setting up the vardeps on write_qemuboot_conf forces the updating of
variables in qemuboot.conf when machine/deploy configuration changes.
This is particularly useful when developing or setting up the qemuboot
(e.g. changing QB_* variables) for new targets or when changing
deployment variables (e.g. KERNEL_IMAGETYPE).
Signed-off-by: Nathan Rossi <nathan@nathanrossi.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
